Partial spreading of adhesive



Feb. 1, 1966 J. w. MANN ETAL 3,232,809

l PARTIAL SPREADING OF ADHESIVE Filed March ll, 1960 2 Sheets-Sheet 1 INVENTOR. fx1/fas l/L//Wa/f/z,

BY J/m M/ 52W/H7 Feb. 1, 1966 .1.w. MANN ETAL 3,232,809

PARTIAL SPREADING OF ADHESIVE Filed March ll, 1960 2 Sheets-Sheet 2 l BB El I5 INVENTOR. Jullus W. MANN JoHN W. SMITH ATTY.

United States Patent O 3,232,809 PARTIAL SPREADING OF ADHESIVE Julius W. Mann, Tacoma, Wash., and John W. Smith,

Lewiston, Idaho; said Smith assiguor to Potlatch Forests, Inc., Lewiston, Idaho, a corporation of Delaware Filed Mar. 11, 1960, Ser. No. 14,413 3 Claims. (Cl. 156-273) Y This invention relates to the spreading Iof adhesive on only a portion of the board that is being prepared for a laminating operation.

More specifically the invention relates to the application of a sheet or layer of glue on one part of the board while leaving the rest of the board devoid of glue so as to facilitate the curing of glue with high frequency, particularly when one edge of a lamination is offset so as to protrude beyond the edges of adjacent laminations.

It is then the purpose of this invention to provide a method for the commercial use of an inexpensive exterior type adhesive in high frequency parallel adhesive curing.

It is the further object to provide laminated wood products using exterior or fully waterproof adhesives at a cost so low that all laminating can be done with exterior adhesives.

It is also an object of the invention to provide a device that readily makes possible the application of glue to a part of the boards surfaced.

The invention will be more fully understood from the following description and the accompanying drawings wherein:

FIGURE l shows a simple inset that can be added t conventional glue spreaders so as to maintain the glue in the reservoir without spillage while at the same time permitting the lumber to have one portion of its face extending beyond the edges of the glue spreader rolls;

FIGURE 2 shows the inset device in use in a conventionad double roll glue spreader;

FIGURE 3 is a perspective View of a board which has had glue spread on both faces but only a part of the faces are spread with glue;

FIGURE 4 shows how the partial spread is effectively utilized in a laminated product with the center piece odset from the top and bottom piece of a three layer product; and

FIGURE 5 is a schematic perspective view illustrating the curing of the adhesive in a high frequency field.

It has been common practice in the past to spread glue in strips or in ribs as with a rubber grooved roll on a glue applicator, but the glue has been spread over the entire width of the board or more generally the present practice is to spread the entire surface of the board and to have the glue layer continuous over the entire surface that has been spread. According to this invention, we spread glue only on a portion of the board, and where it is spread the glue layer is continuous although it can also be spread in ribs or strips, particularly in that area Where the faces of the board in the final laminated product will be abutting each other.

In preparing wood for one type of laminating, such as laminated roof decking where it is desirable to form a tongue and groove, the product may be made by three layers of lumber with the center layer offset some distance, for example, M of an inch, to provide a tongue on one edge and a groove on the other edge. In the process it is most practical to apply glue to both faces of the center piece. In making this glue application we have found that it is advantageous to spread the glue only on the portion of the faces which will be in contact with the faces of the other two lumber layers in the product. By this means, where high frequency parallel 3,232,809 Patented Feb. 1, 1966 ICC glue curing is used, no adhesive is in contact or comes in contact with the electrodes. In addition, where one piece is offset from the others, the phenolic glue exposed to the air within the high frequency field where the glue spread surface extends beyond the area of actual contact between adjacent pieces emits gases and vapors that quickly cause arcing in the electronic field. Said gases and vapors are not evolved from phenolic glue between `abutting faces of the layup in sufhcient amounts to cause -trouble because of the dry wood absorbing them. In

the practice of this invention great care is exercised to avoid exposing any glue on the protruding faces of offset pieces. As a result of these practices it becomes possible to cure alkaline catalyzed phenolic adhesive in parallel with the high frequency field which heretofore has been impossible because the phenolic adhesive is an arc tendency type of adhesive that makes impossible the use of the parallel bonding technique where former methods of glue spread were used. This method permits the curing of the alkaline catalyzed phenolic glue without arcing.

In preparing the wood for this operation it is important first that it be seasoned carefully so that it has uniform moisture content and preferably a maximum moisture content of 12%, in order to reduce the curing time to the least possible interval. Thereafter it is important that a high quality surfacing job be applied to the faces of the lumber. In many lumber manufacturing operations the planers are run too fast or inadequately maintained with the result that poor surfacing of the lumber is accomplished which reduces the benefits from this type of gluing. However, when this system is used it is now possible to provide exterior type of waterproof glue bonds with the least expensive exterior type adhesive that is available, that is, a high temperature setting or alkaline catalyzed phenol-formaldehyde adhesive. Prior to the development of this invention, no commercial application of parallel bonding of phenol-formaldehyde wood adhesives had been practiced.

The drawings illustrate how a conventional glue spreader is connected to provide for the partial glue spreading operation. The guide 10 and attached parallel spacer 10a provided at the ends of the spreading rolls 11 and 12 are moved back and a soft metal insert 13 is provided adjacent to the end of the lower glue bearing roll 12. The portion 15 of the board 14 that is not to receive glue rides over the insert 13. A fiber seal 18 is provided on the insert adjacent to the roll 12. This construction allows the board 14 to protrude beyond the ends of the rolls 11 and 12 the desired amount.

When a core board 14 is coated with glue on both sides it is laid between two like boards 16 and 17 that have no glue on them so that the glue covered face portions of the board 14 are completely covered by the boards 16 and 17. Now when the high frequency charge is applied across the boards from right tot left, parallel to the glue line, there is no exposed glue surface to emit the damaging gases and vapors. This is true of the inner exposed faces of the groove at one side edge of the unit as well as the three exposed surfaces of the tongues of the unit.

The method of curing the adhesive is illustrated in the perspective view shown in FIGURE 5. The laterally offset boards 14, 16 and 17 are placed between electrodes 20 and 21 and are subjected to end pressures designated schematically by the arrows 22. The center board 14 has glue or adhesive spread thereon and designated as the glue line 23. The bare areas of board 14 are shown by the numeral 15 and do not abut the adjacent boards 17 and 16. Thus only those surface areas of board 14 which abut the adjacent laminates or boards 16 and 17 are covered with the adhesive which is to join the boards 14,

f product.

16 and 17 as a unit. A high frequency field is then provide exterior or waterproof glue lines costing inthe range of $2.00 to $3.00 per thousand bd. ft. of glued Previously, however, in order to obtain an equally satisfactory and acceptable-exterior glue bond the cost ofthe glue line has been in the range of $15.00 a thousand bd. ft. which has only been obtainable by the use of suchadhesivcs as phenol-resorcinal or melamineformaldehyde or combinations thereof. This new procedure combined with appropriatetechniques of preparing lumber and applying high-frequency parallel'bonding for the curing of the glue has made it possible to providefthe user of Wood a laminated product with exterior glue lines at greatly reduced cost. In fact, this type of gluing to give glue bond suitable for exterior use is less expensive 'than many types of gluing that are limited to interior use.

The art of gluing and the patents have previously revealed the use of an air gap or a solid layer between electrodes andthe glue line, however, there has been no known successful practice of the application'of this art with phenolic glues until the partial glue spread invention was added to the art. Thus, while it is a parallel high frequencybonding technique it is an improvement in the parallel bonding of glues kas adjusted to the conditions described.

We claim as our invention:

1. In a process for producing a wood laminate having a plurality of sandwiched laminae having a maximum moisture content of l2 percent secured to one another by an adhesive wherein the adhesive is cured in a high frequency field parallel to the glue line:

the step of spreading a waterproof exterior grade alkaline catalyzed phenol-formaldehyde adhesive onto a` high quality finished surface of a lamina prior to joinder of said surface to a like mating surface of an adjacent lamina, the spreading of said adhesive being carried out continuously over a surface -area less` than the total surface area of the lamina surface on which it is applied, a surface strip of constant width adjacent one side edge ofthe lamina and extending along the full length of the lamina surface on which the adhesive is applied being maintained free of adhesive.

2. In a process for producing a wood laminate having a plurality of sandwiched laminae having a maximum moisture content of 12 percent of equal widthwherein adjacent laminae are laterally offset from one another, and wherein the adhesive is cured in ahigh frequency field parallel to the glue line:

the step of spreading a waterproof exterior grade alkaline catalyzed phenol-formaldehyde adhesive onto a high quality finished surface of a lamina prior to joinder of said surface toa mating surface of an i adjacent lamina, the spreading of .said adhesive being confined to the surfacearea to'be abutted by lsaid adjacent lamina in the assembled laminate.

3. In a process for-'producing a wood laminate having at least three sandwiched laminae of equal width having thigh quality 'finished `mating surfaces land a maximum fmoisture content of l2 percent, wherein adjacent laminae are laterally offset from one another tofform complevmentary tongue -and groove fconfigurationsat each side -of'the laminate and wherein the adhesive is-cured in a :high-frequency fieldparallel to the glue lines:

the step of spreading a` waterproof `exterior grade alkaline catalyzed phenol-formaldehyde adhesive onto a 'first one1of 'each pair offmatingsurfaces on adjacent laminae prior to kjoinder ofthe laminae,'-'the spreading of :said adhesive being confined to the surface areas to be abutted by adjacent laminae in the assembled laminate;

a-nd subsequently curing said adhesive in Iaihigh 'frequencyfield directed parallelto theprespective glue lines.

References Cited by the Examiner UNITED STATES PATENTS 2,390,087 `12/1945 Fink .20--5 2,434,573 1/1948 Mannet al v154-126 2,457,498 12/1948 Russell et al 156-4273 2,591,771 4/1952 Bergey 1156---273 2,675,838 4/.1954 Hickok et al 144--279 2,981,652 4/1961 Peterson et al 156-310 3,016,316 1/1962 Olson .156-293 XR 3,038,511 6/1962 Smith 144-281 OTHER REFERENCES Russell kand Mann: Radio-Frequency Technology in Wood Application,Transactionsof lthe A.S.M.E.,"August 1944, pp. 563-567. (TJ LA7.)

EARL `M. BERGERT, P111ary-Examl1er.

vCARL F. KRAFFT, ALEXANDER `WYMAN,

Examiners. 

1. IN A PROCESS FOR PRODUCING A WOOD LAMINATE HAVING A PLURALITY OF SANDWICHED LAMINAE HAVING A MAXIMUM MOISTURE CONTENT OF 12 PERCENT SECURED TO ONE ANOTHER BY AN ADHESIVE WHEREIN THE ADHESIVE IS CURED IN A HIGH FREQUENCY FIELD PARALLEL TO THE GLUE LINE: THE STEP OF SPREADING A WATERPROOF EXTERIOR GRADE ALKALINE CATALYZED PHENOL-FORMALDEHYDE ADHESIVE ONTO A HIGH QUALITY FINISHED SURFACE OF A LAMINA PRIOR TO JOINDER OF SAID SURFACE TO A LIKE MATING SURFACE OF AN ADJACENT LAMINA, THE SPREADING OF SAID ADHESIVE BEING CARRIED OUT CONTINUOUSLY OVER A SURFACE AREA LESS THAN THE TOTAL SURFACE AREA OF THE LAMINA SURFACE ON WHICH IT IS APPLIED, A SURFACE STRIP OF CONSTANT WIDTH ADJACENT ONE SIDE EDGE OF THE LAMINA AND 